The present invention relates to a liquid crystal display which in particular regulates the light of a backlight of a personal computer using a regulating current type inverter.
As shown in FIG. 1, a conventional liquid crystal display is constituted of a display control circuit 1, a liquid crystal display section 3, a backlight 4 and an inverter 5.
At the above mentioned construction, the display control circuit 1 displays the display contents which the personal computer (the personal computer is not described in FIG. 1) indicates to display on the liquid crystal display section 3. In this case, the liquid crystal display section 3 makes the adjustment of the display luminance possible by regulating the backlight by the inverter 5.
The Japanese Patents Laid-Open Publication No. HEI 6-34946 and HEI 8-179276 disclose the method which controls the backlight using a regulating current type inverter.
In the above mentioned conventional type liquid crystal display, at the case that the backlight of the liquid crystal display is turned on by the regulating current type inverter, the stability of fluorescent lamp is required while the light is on and the current must not be decreased below a certain level. Therefore, there is a problem that a user can not make the display luminance dark being below a certain level, even the user wants to have such a dark display luminance.
In this case, it is possible that a PWM (pulse width modulation) type inverter makes the display luminance darker, however the inverter circuit becomes complex.
It is therefore an object of the present invention to provide a liquid crystal display which solves the above mentioned problem and makes not the construction of the inverter complex and makes the change of the display luminance being wider than the regulating light range of the inverter possible.
The liquid crystal display of the present invention provides a luminance regulating means which regulates the light of the backlight disposed at the back of the liquid crystal display section using a regulating current type inverter and controls the display luminance of display data of the liquid crystal display section by changing the gradations of display data to be displayed on the liquid crystal section low responding to an external instruction.
That is, the liquid crystal display of the present invention makes the regulation of display brightness possible by not changing the brightness of the backlight in the liquid crystal display and by implementing the operation for the image signal data.
Concretely, the display luminance is regulated by the backlight whose regulating light is controlled by an inverter for the liquid crystal display section. The liquid crystal display section displays the image signals formed at a display control circuit and made the display gradations low at the luminance regulating circuit. With this, it is possible that the display luminance is controlled wider than the possible range of the regulating light by the backlight of the liquid crystal display.
According to a first aspect of the present invention, for achieving the above mentioned objects, at a liquid crystal display which regulates the light of a backlight disposed at the back of a liquid crystal display section using a regulating current type inverter, there is provided a luminance regulating means for controlling a display luminance of display data at said liquid crystal display section, by changing gradations of the display data displaying on said liquid crystal display section to low values responding to an external instruction.
According to a second aspect of the present invention, at the liquid crystal display, said luminance regulating means provides a shift means for shifting said display data and a switching means which selects either an output of said shift means or said display data responding to said external instruction and outputs the selected one on said liquid crystal display section.
According to a third aspect of the present invention, at the liquid crystal display, said luminance regulating means is constructed to implement the control of said regulating current type inverter working together with the control of said display luminance.
According to a fourth aspect of the present invention, at the liquid crystal display, said luminance regulating means provides a luminance setting means which outputs the switching instruction for said switching means and the regulating light instruction for said regulating current type inverter responding to said external instruction.
According to a fifth aspect of the present invention, at the liquid crystal display, said luminance regulating means provides an arithmetic calculation means which operates said display data with a setting value responding to said external instruction.
According to a sixth aspect of the present invention, at the liquid crystal display, said luminance regulating means is constructed to implement the control of said regulating current type inverter working together with the control of said display luminance.
According to a seventh aspect of the present invention, at the liquid crystal display, said luminance regulating means provides a control means for controlling said arithmetic calculation means and said regulating current type inverter respectively responding to said external setting value.